1. Field of the Invention
The present invention relates to a receptacle cage, a receptacle assembly, and a transceiver module assembly.
2. Description of the Related Art
In an optical communication system, a transceiver module has been put into practical use in order to transmit an optical signal transmitted through an optical connector and the like to a mother board. As disclosed in Japanese Patent Laid-Open No. 2005-520296, for example, such a transceiver module is located on a chassis which constitutes a communication system. The transceiver module comprises the following constituents as main elements, namely, an optical module (which is referred to as a module assembly in Japanese Patent Laid-Open No. 2005-520296), and an optical module receptacle (which is referred to as a receptacle assembly in Japanese Patent Laid-Open No. 2005-520296) mounted on a circuit board serving as a mother board and configured to detachably accommodate the optical module.
An optical cable connector and an optical cable for establishing interconnection with another system, for example, are connected to a port at an end portion of the optical module exposed to a front cover of the chassis. When the optical module is connected to the optical module receptacle, a portion being connected of the optical module is connected to a connected portion of a receptacle connector mounted on a portion of the circuit board inside the optical module receptacle. The portion being connected of the receptacle connector is electrically connected to the above-mentioned circuit board. Hereby, the optical cable connector and the optical cable are electrically connected to the circuit board via the transceiver module.
Moreover, as disclosed in Japanese Patent Laid-Open No. 2005-520296, a looped EMI gasket collar and resilient metal spring gaskets are provided as a countermeasure for radio wave interference (electromagnetic interference, or EMI) in the periphery of a module insertion slot of the optical module receptacle in the transceiver module. In addition, multiple EMI gaskets are provided respectively on a front edge as well as two side edges of a lower opening, which is formed in the vicinity of the receptacle connector inside the optical module receptacle. Herewith, an EMI shield is formed at a junction between the receptacle connector and the optical module.
Further, as also disclosed in Japanese Patent Laid-Open No. 2005-520296, a measure for heat dissipation has been proposed that a heat sink may be provided on an upper surface of the optical module receptacle in the transceiver module.
In the above-described countermeasure for the radio wave interference, unnecessary radiation of noise from the inside of the transceiver module located in the chassis to the inside of the chassis is harmful to other electronic components on the circuit board as well. Accordingly, it is also required to inhibit such noise radiation into the chassis through a gap between an outer peripheral portion of the optical module and an inner peripheral portion of the optical module receptacle.
Japanese Patent Laid-Open No. 2005-520296 discloses a proposal of the configuration in which the multiple EMI gaskets are provided respectively on the front edge as well as the two side edges of the lower opening formed in the vicinity of the receptacle connector in the optical module receptacle.
However, a gap is formed between an upper surface portion at the outer peripheral portion of the optical module in the optical module receptacle and the inner peripheral portion of the optical module receptacle opposed to the upper surface portion. In particular, a given amount of a relative play in a direction of attaching or detaching the optical module is provided between the optical module and the optical module receptacle. Accordingly, it is not easy to tightly seal the gap between the outer peripheral portion of the optical module and the inner peripheral portion of the optical module receptacle. In short, the above-described configuration proposed in Japanese Patent Laid-Open No. 2005-520296 is likely to cause noise radiation through the gap and is therefore insufficient in light of the countermeasure for the radio wave interference.